Mount an Ennoid MK8 controller in a GT box without a metal CNC plate. Has room for buzzer & Ava Spark Buck converter. Use M3 bolt and washer to mount to stock GT/GTS box. Hot glue to secure the buzzer and buck converter. Tolerance is tight, so thermal paste between the box and controller is recommended. Maybe a thin thermal pad will work also.

I remixed and combined multiple files to make this. Buzzer is Seed Studio Buzzer. STEP and STL included